One objective of this study is to identify, isolate and chemically characterize the protein (or proteins) on the surface of the sea urchin egg that is involved in specifically binding sperm prior to fertilization. A second objective is to characterize the molecular components of an isolated cell surface complex of the sea urchin egg that consists of the plasma membrane and attached cortical vesicles. The membrane and the vesicles have been separated and currently the components of each are being studied. In addition we plan to utilize the complex to study biochemical changes that may be involved in secretion.